In a groundbreaking new study published in Nature Communications, researchers present compelling evidence that the Paleocene–Eocene Thermal Maximum (PETM) — a rapid global warming event occurring approximately 56 million years ago — inflicted profound losses on vegetation functioning worldwide. This revelation not only reshapes our understanding of past climate-vegetation dynamics but also carries alarming implications for current and future ecosystems facing anthropogenic climate change.
The PETM is characterized by a swift and dramatic spike in Earth’s surface temperatures, with estimates suggesting a global average temperature increase of 5 to 8 degrees Celsius within a few thousand years. This extraordinary warming phase is widely regarded as an analog for modern-day climate trajectories, driven predominantly by massive carbon injections into the atmosphere and oceans. The new study meticulously reconstructs the functional ecology of terrestrial plants during this interval, revealing a marked deterioration in vegetation roles that underpinned terrestrial ecosystem stability.
By integrating paleoecological proxies, isotope geochemistry, and advanced Earth system modeling, the researchers uncovered multifaceted disturbances in plant physiological processes. Photosynthesis, water regulation, and nutrient cycling — key functions that maintain ecosystem productivity and resilience — exhibited significant reductions. These functional impairments manifested as decreased carbon sequestration potential and altered hydrological cycles, providing crucial insights into how vegetation may respond to rapid climatic perturbations.
The team employed stomatal index analysis — a proxy derived from fossilized leaf structures — as a primary indicator of plant physiological stress during the PETM. They observed a consistent decline in stomatal density worldwide, suggesting that plants reduced gas exchange to conserve water under heightened thermal stress and increased atmospheric CO₂ levels. This physiological adjustment, while protective in the short term, compromised photosynthetic rates and dampened carbon uptake, which in turn exacerbated global carbon cycle feedbacks.
Moreover, isotopic signatures from paleosol carbonates and organic matter indicated shifts in plant community composition and productivity. There was a pronounced transition from woody gymnosperms to herbaceous angiosperms in many regions, reflecting both thermal tolerance limits and drought-induced stresses. Such vegetation turnover events fundamentally altered biome distributions, with tropical forests retreating and more arid-adapted ecosystems advancing, echoing patterns predicted for future climate scenarios.
The implications of these findings extend beyond paleobotany, illuminating cascading effects on ecosystem structure, biodiversity, and biogeochemical cycling. Loss of vegetation functionality during the PETM likely contributed to soil degradation, reduced habitat complexity, and nutrient imbalances, triggering feedback mechanisms that intensified climatic disruption. Understanding this interplay is pivotal for refining predictive models that aim to forecast ecosystem responses under contemporary warming.
Importantly, the research underscores the vulnerability of terrestrial ecosystems to swift temperature elevations, particularly when accompanied by increased CO₂ concentrations and hydrological stress. The PETM serves as a natural experiment demonstrating that even robust, ancient forest systems were susceptible to functional decline when pushed beyond ecological thresholds. This challenges previous assumptions that elevated CO₂ could universally promote vegetation growth, highlighting nuanced physiological constraints.
The study also details spatial heterogeneity in vegetation responses, noting that equatorial and mid-latitude biomes exhibited differential resilience patterns. Local climatic variables such as precipitation regimes and seasonal temperature extremes modulated the severity of functional losses. Such regional variability underscores the complexity of biological responses to climate perturbations and calls for high-resolution paleoenvironmental reconstructions to properly gauge ecosystem trajectories.
Beyond the terrestrial sphere, diminished vegetation functionality during the PETM likely altered atmospheric composition in ways that intensified global warming. Reduced net primary productivity decreased carbon sinks, prolonging atmospheric CO₂ residence times and amplifying the greenhouse effect. This feedback loop underscores vegetation’s critical role as both a driver and moderator of Earth’s climate system.
The research team also bridges geological data with modern plant physiological studies, identifying convergent patterns of stress response. For example, the stomatal conductance reductions observed during the PETM echo mechanisms seen in contemporary plants subjected to drought and heat stress. Such parallels validate the use of fossil proxies in reconstructing ancient physiological processes and enrich our understanding of plant adaptability limits.
In their discussion, the authors emphasize the urgency of integrating paleoecological insights into current climate impact assessments. The PETM, as an analogue for rapid warming, reveals thresholds beyond which vegetation degradation may become inevitable, with profound repercussions for ecosystem services such as carbon storage, water regulation, and soil stabilization.
The comprehensive dataset compiled for this study — spanning multiple continents and diverse paleoecosystems — represents a significant advancement in Earth system science. It highlights the necessity of multidisciplinary approaches combining paleoclimatology, paleoecology, and biogeochemistry to unravel the intricate feedbacks between vegetation and climate.
As anthropogenic warming accelerates in the 21st century, this research serves as a stark reminder of vulnerability intrinsic to terrestrial ecosystems. Despite physiological plasticity and evolutionary adaptation, the fundamental functions of vegetation can be compromised under sustained thermal and hydric stress, potentially triggering ecosystem collapse scenarios reminiscent of the PETM.
In sum, the paper authored by Rogger, Korasidis, Bowen, and colleagues provides a detailed reconstruction of vegetation functional losses during one of Earth’s most significant hyperthermal events. Their findings advance paleoclimatic science substantially, while simultaneously serving as a cautionary tale for contemporary climate futures. The interplay between rapid warming and terrestrial biosphere functions emerges as a critical nexus for research and conservation efforts.
The revelations from this study underscore the need to prioritize ecosystem resilience-building strategies, including conservation of genetic diversity and restoration of degraded landscapes. Understanding past vegetation responses enables better forecasting, guiding policy and management interventions to mitigate or avert similar functional collapses in modern ecosystems.
The paper’s integration of fossil record analysis with mechanistic models and physiological proxies provides a template for future paleoclimate research, encouraging a holistic perspective on how ancient biota navigated extreme environmental changes. Such frameworks will be invaluable as we confront an uncertain climatic horizon marked by unprecedented rates of change.
With this enhanced knowledge of how vegetation function faltered during the PETM, scientists and environmental stakeholders gain critical perspective on the fragility of Earth’s biosphere under rapid warming. The implications resonate across disciplines, reinforcing the indispensability of long-term ecological data in framing the future trajectory of life on our warming planet.
Subject of Research: Vegetation functional changes and ecosystem impacts during the Paleocene–Eocene Thermal Maximum (PETM).
Article Title: Loss of vegetation functions during the Paleocene–Eocene Thermal Maximum.
Article References:
Rogger, J., Korasidis, V.A., Bowen, G.J. et al. Loss of vegetation functions during the Paleocene–Eocene Thermal Maximum. Nat Commun (2025). https://doi.org/10.1038/s41467-025-66390-8
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